Non-Hodgkin's lymphoma (NHL) is an increasing cause of death among people with acquired immunodeficiency (AIDS) due to declining rates of opportunistic infection (OI) with the use of highly active antiretroviral therapy (HAART). While the prognosis of AIDS- related NHL has been poor in the past, HAART may improve outcomes. Specific Aims: 1) We will identify NHL patients with and without AIDS from the population-based cancer registry using a rapid case ascertainment method. 2) We will describe HIV-specific patient and treatment characteristics of AIDS-NHL patients and distinguish which factors influence prognosis. 3) We will describe tumor characteristics and cancer treatment in NHL patients with and without AIDS and distinguish which oncologic features influence prognosis. 4) We will determine how the use of HAART influences the International Prognostic Index (IPI) and form an original prognostic model. Research Design: Using rapid case ascertainment, we will contact all AIDS-NHL cases reported in a two-year period to the cancer registry for Orange, San Diego, and Imperial Counties and a sample of non- AIDS NHL cases matched on age, sex and race/ethnicity reported during the same two-year period. We will perform interviews and chart reviews on NHL patients to collect information on biologic factors that influence prognosis such as such as NHL site, stage, and pathologic grade as well as patient-specific features such as race/ethnicity, performance status, and health care access. We will gather data on HIV-specific features including CD4 cell count, HIV viral load, HIV risk factors, and use of HAART for NHL patients with AIDS. We will compare survival, development of co-morbidities/OI, and quality of life (QOL) between NHL patients with and without AIDS over a three-year follow-up period between AIDS patients who receive HAART and those who do not. Lastly, we will determine how the use of HAART influences the IPI and develop a prognostic model that incorporates HIV-related factors, tumor characteristics, HAART, and chemotherapy.